cue ball roundness

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SPetty

AzB Silver Member
Silver Member
Or spherical-ness...

My friend has a cue ball that rolls a little off sometimes.

I think there may be two possible reasons that a cue ball would do that:
1) the center of gravity weight isn't quite in the center
2) the cue ball isn't quite perfectly round or sphere-shaped

It's an Aramith green logo magnetic ball.

It looks unround to me, but you know that vision is sometimes deceiving, and I might be imagining it. :p

Any suggestions on how to test what the problem might be? It's not necessary to know the answer, but it would be a fun thing to learn.

TIA
 
pt109

pt109

WO double hemlock
Silver Member
It would be a miracle if a magnetic ball rolled true....in my experience.

Bypass the whole problem by playing on Diamond bar tables with tournament balls.
 
Skratch

Skratch

AzB Silver Member
Silver Member
SPetty said:
Or spherical-ness...

My friend has a cue ball that rolls a little off sometimes.

I think there may be two possible reasons that a cue ball would do that:
1) the center of gravity weight isn't quite in the center
2) the cue ball isn't quite perfectly round or sphere-shaped

It's an Aramith green logo magnetic ball.

It looks unround to me, but you know that vision is sometimes deceiving, and I might be imagining it. :p

Any suggestions on how to test what the problem might be? It's not necessary to know the answer, but it would be a fun thing to learn.

TIA
Click to expand...

Assuming the ball is perfectly round: Spin it and mark the top of the ball when it settles. Rotate the ball in another direction and spin it again a few times, and again mark the top. If it appears to mark the same spot, the CG isnt centered.

Assuming the ball isnt round: Measure the outer edges in several axes. (imagine the cue ball is the shape of a cube and you're measuring opposite faces). If all the measurements are the same, then its round.

Anyone else have any ideas?
 
P

Prince H

AzB Silver Member
Silver Member
Assuming it is supposed to be the same size as the object balls, place 3 balls next to each other on the rail, with two object balls on the outside and the suspicious cueball as the middle ball. Then lay a flat edge of some kind on top of the all three. You can then look at the contact points and all three balls should be touching the flat edge. Then rotate the cue ball around and you should notice any spots that are slightly wider or thinner.
 
P

Prince H

AzB Silver Member
Silver Member
...and after thinking about it more, it is possible that the ball is actually round, but that the center of mass is off...in which case my previous post might not give you the answer you need.
 
L

louieatienza

AzB Silver Member
Silver Member
To see if the CG is truly in the center, you could make a makeshift do-do scale like used in bowling, mark the octants on the CB, and compare the weights of each half against the other.

The spin technique should work; better would be to set up a rig with four ball bearings, 2 a side like a cue spinner, spin the CB along the same radial axis as the ball bearings and mark the axis point of the ball, and compare it, moving said axis point to see if it migrates to the same spot. You could also possibly do the test on some liquid that would hold the CB buoyant.

To test roundness, you could use the same ball bearing rig, but place it under a test indicator held on a stand. You'd have to use ABEC7 bearings to ensure good accuracy. I'd mark the CB in grid fashion and take readings at different locations; you can map out likely where the CB's shape varies.

Another thing to note that if the CG is truly off, and the CB eventually rolls in a "preferred spin axis" then it would likely wear perpendicular to that axis, at least more so than anywhere else...

I should note that there are non-spherical shapes that exhibit similar properties to a circle (they look like pyramids with rounded points and edges) so the above measuring rig actually only measures change in CB "diameter" along its surface...
 
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Skippy27

AzB Silver Member
Silver Member
Find a truly flat surface and put a piece of glass down. Set the ball on it and let it settle. Mark the top. Do it again and mark it again. Do it a third time and mark it again. It it constantly goes to the same spot or you see as it settling it is wobbling then it is probably having some issues and should be replaced.

Aramith balls are very good, even their ones for magnetic returns (regardless of what some say here). They have a higher end purple logo one that is suppose to be a very accurate roller as it has iron distributed throughout it evenly. I think those run around $24.
 
Frankenstroke

Frankenstroke

2 Gus Szamboti cues
Silver Member
ShakesSea said:
I've never heard of carrying your own magnetic cueball. Seems equivalent to carrying your own one piece bar cue with no tip.
Click to expand...

I carry my own magnetic cueball. Aramith purple logo. Better than what the bars offer. Most league team captains in my area bring an Aramith.
 
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bobprobst

AzB Silver Member
Silver Member
Skratch said:
Assuming the ball is perfectly round: Spin it and mark the top of the ball when it settles. Rotate the ball in another direction and spin it again a few times, and again mark the top. If it appears to mark the same spot, the CG isnt centered.
Click to expand...

This is correct. On the second spin, set the top mark just slightly above the equator and you should be able to see it migrate back to the top.

Will be most precise on a very slick surface.
 
R

Renegade_56

AzB Silver Member
Silver Member
It's a magnetic cue ball, so there is a magnet inside, which is not perfectly centered obviously. Get a different cue ball is the only real solution I think.
 
S

SPetty

AzB Silver Member
Silver Member
Thanks y'all!

Thanks, everyone, for the ideas.

I already knew about the ball-within-a-ball manufacturing, and the layer of metal flakes material, but I didn't think that in and of itself would be the problem. Most green logo Aramith balls seem to roll good and true.

I like the spin on glass idea - as the spin slowly slows down, the heavy spot should go to the bottom. What if there was a slight bow in the glass - wouldn't that encourage it to settle heavy side down even more? Or maybe a glass bowl?

I like the "put the ball between balls idea", but this "little off" is so subtle most of the time that it could be difficult to find a high/low spot. But I'll try it.

My friend didn't believe me for a little while that there was a problem with the ball, but he finally experienced it enough once he was watching for it that he couldn't tolerate using it any more. So he gave it to me. Once the "analysis" is complete, I think I could talk him into hitting it with a hammer to see what's inside! (So on a side note - is there a favorite place to get a new Aramith green logo cue ball?)

louieatienza: Wow, those are all great ideas (and now I know what a "dodo scale" is), but more trouble than I really wanted to go through for this - I'd rather hit it with a hammer! :)

randyg: I sent you a "Howdy" via one of your teammates a few weeks ago. Hope you got it!
 
goettlicher

goettlicher

AzB Silver Member
Silver Member
SPetty said:
Thanks, everyone, for the ideas.

I already knew about the ball-within-a-ball manufacturing, and the layer of metal flakes material, but I didn't think that in and of itself would be the problem. Most green logo Aramith balls seem to roll good and true.

I like the spin on glass idea - as the spin slowly slows down, the heavy spot should go to the bottom. What if there was a slight bow in the glass - wouldn't that encourage it to settle heavy side down even more? Or maybe a glass bowl?

I like the "put the ball between balls idea", but this "little off" is so subtle most of the time that it could be difficult to find a high/low spot. But I'll try it.

My friend didn't believe me for a little while that there was a problem with the ball, but he finally experienced it enough once he was watching for it that he couldn't tolerate using it any more. So he gave it to me. Once the "analysis" is complete, I think I could talk him into hitting it with a hammer to see what's inside! (So on a side note - is there a favorite place to get a new Aramith green logo cue ball?)

louieatienza: Wow, those are all great ideas (and now I know what a "dodo scale" is), but more trouble than I really wanted to go through for this - I'd rather hit it with a hammer! :)

randyg: I sent you a "Howdy" via one of your teammates a few weeks ago. Hope you got it!
Click to expand...


Yes I did. Howdy back my friend.
 
kid

kid

billiard mechanic
Silver Member
Hitting it with a hammer will probably just dent it a bit. They withstand 5t of pressure before cracking. Cutting is the way to go if you wan't to see what's inside


Envoyé de mon iPhone en utilisant AzBilliards Forums
 
S

SPetty

AzB Silver Member
Silver Member
kid said:
Hitting it with a hammer will probably just dent it a bit. They withstand 5t of pressure before cracking. Cutting is the way to go if you wan't to see what's inside
Click to expand...
Or I can find someone with a shop press or I can use my 7 ton log splitter! I don't want to see the center, but I want to see what ball number, if any, is used under the metal. The way it acts possessed, it's probably the 13!
 
Bob Jewett

Bob Jewett

AZB Osmium Member
Staff member
Gold Member
Silver Member
I think the easiest (and best) way to test for roll-off is to shoot lags from the head spot and try to return to the head spot. Mark an arrow on the ball with a pencil. Shoot lag shots with each of the following positions:

1. Arrow on top, pointed forward
2. Arrow on top, pointed backward
3. Arrow on top, pointed left
4. Arrow on top, pointed right
5. Arrow on left side
6. Arrow on right side

This procedure eliminates the effect of table roll if you compare the difference between each corresponding pair of lags. It will also tell you the "heavy" side of the cue ball for an off-center ball. I developed this test when I was practicing my lags with my own blue-circle cue ball. One time it would roll off six inches to the left and the next six inches to the right.

A misshapen ball is harder to test. I have a ball gauge that is two round holes in a steel plate. It can find, for example, a bulging eye on an object ball. The roll test above might not happen to hit the bulge.
 
Dave-Kat

Dave-Kat

AzB Silver Member
Silver Member
Due to my OCD, I used to have a golf ball gauge back in the day to check for any out of round imperfections on used 'players'. You would pass the golf ball through center and rotate and look for 'light' or uneven spots. Simple and efficient.

If ball failed, to the 'Shag Bag' they went :groucho:

If you suspect that the said cue ball is out of round I would replace it immediately to eliminate the possibility of the 'thought' coming into mind mid-stroke.

Have a good weekend,

-Kat,
 
S

SPetty

AzB Silver Member
Silver Member
I couldn't determine that the cue ball was off-weighted, but I did find evidence that it is out of round... I am so sorry, I didn't know the pictures would be so big, and I can't figure out how to delete the post to try again...

Two posts later, Bob Jewett helped me out with the pics. I deleted them here. Thanks Bob!
 
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